Reverse gate for water jet propulsion system

ABSTRACT

A non-steerable reverse gate having a structure which reverses the lateral flow component when the steering nozzle is turned. The reverse gate produces high reverse and steering thrusts, while requiring low operating loads. The steering response in reverse is the same as an outboard or inboard/outboard. In effect, the transom thrusts to the side that the steering wheel is turned to. The reverse gate has a pair of flow-reversing passages for providing reverse thrust, a lateral steering passage for producing a lateral thrust when the steering nozzle is turned, and a fixed or pivotable central deflector body. The deflector body has three vertical walls connected to a juncture. One vertical wall is straight and extends forward of the juncture. The other vertical walls are curved and extend rearward and laterally outward from the juncture on opposite sides of a plane of symmetry. Each curved vertical wall has a flow-deflecting surface which is concave and faces a front opening of the reverse gate. The straight vertical wall splits the incoming flow into two streams, while the flow-deflecting surfaces divert portions of the respective streams toward the respective flow-reversing passages. Steering in reverse is provided by water which flow around the deflector body and out a discharge opening of the lateral steering passage.

FIELD OF THE INVENTION

[0001] This invention generally relates to water jet apparatus forpropelling boats and other watercraft. In particular, the inventionrelates to mechanisms for shifting a water jet apparatus to selectivelypropel a craft in the forward or reverse direction.

BACKGROUND OF THE INVENTION

[0002] It is known to propel a boat or other watercraft using a waterjet apparatus mounted to the hull, with the powerhead being placedinside (inboard) the hull. An impeller is mounted on a shaft driven by adrive shaft of the motor, and is housed in a duct having an inlet and anoutlet. The impeller is designed such that during motor operation, therotating impeller impels water rearward through the duct. The waterdischarged from the duct outlet produces a thrust which propels the boatforward.

[0003] In addition, it is known to provide a mechanism for diverting thedischarged water flow to one side or the other of a midplane, therebyenabling the boat operator to steer the boat to the left or right duringforward propulsion. One such mechanism is a steering nozzle pivotablymounted to the duct and in flow communication with the duct outlet.Preferably the pivot axis of the steering nozzle lies in the midplane.As the steering nozzle is pivoted to the left of a central position, thewater flow out of the duct is diverted leftward, producing a thrustwhich pushes the water jet apparatus and the boat stern to the right,thereby causing the bow of the boat to turn to the left. Similarly, theboat bow turns to the right when the steering nozzle is pivoted to theright of the central position.

[0004] It is also known to provide a mechanism for reversing thedirection of the water flow exiting the steering nozzle. The reversegate can be pivotably mounted to the steering nozzle, its pivot axisbeing generally perpendicular to the pivot axis of the steering nozzle.In the up position, the reverse gate is clear of the water flow exitingthe steering nozzle. In the down position, the reverse gate is disposedin the path of the exiting water flow. In its simplest embodiment, thereverse gate has a U-shaped channel which reverses the water flowexiting the steering nozzle. In other words, when the steering nozzle isturned to the left, the resulting water flow having rearward andleftward flow components is redirected by the reverse gate to haveforward and rightward components. This produces a thrust which pulls theboat rearward and propels the water jet apparatus and boat stern to theleft, causing the boat to turn left during rearward movement. Similarly,the boat turns to the right during rearward movement when the steeringnozzle is turned to the right. The provision of a steerable reverse gateallows the boat operator to steer in forward and reverse in the samemanner that an automobile can be steered.

[0005] In accordance with other known designs, the reverse gate is notsteerable, i.e., the reverse gate is pivotably mounted to the water jethousing. In the up position, the reverse gate is clear of the water flowexiting the steering nozzle; in the down position, the reverse gateobstructs the water flow exiting the steering nozzle and reverses therearward flow component. Some non-steerable designs also reverse thelateral flow component; others do not. The non-steerable reverse gatedesigns which reverse the lateral flow component cause therearward-moving boat to turn left when the steering nozzle is turned tothe left and to turn right when the steering nozzle is turned to theright. However, these prior designs provide less than optimal reversethrust and steering thrust. There is a need for a non-steerable reversegate which reverses the lateral flow component, provides increasedreverse and steering thrusts, and operates with low cable loads.

SUMMARY OF THE INVENTION

[0006] The present invention is directed to a non-steerable reverse gatehaving a structure which reverses the lateral flow component when thesteering nozzle is turned. The reverse gates in accordance with thepreferred embodiments produce high reverse and steering thrusts, whilerequiring low operating loads. The steering response in reverse is thesame as an outboard or inboard/outboard. In effect, the transom thruststo the side that the steering wheel is turned to. The invention is alsodirected to a water jet propulsion system having a non-steerable reversegate of the foregoing type.

[0007] In accordance with one preferred embodiment of the invention, thereverse gate comprises a pair of flow-reversing passages for providingreverse thrust, a lateral steering passage for producing a lateralthrust when the steering nozzle is turned, and a fixed central deflectorbody. In accordance with another preferred embodiment, the centraldeflector body is pivotable about a vertical axis.

[0008] In accordance with both preferred embodiments disclosed herein,the flow-reversing passages are located on opposite (i.e., port andstarboard) sides of the reverse gate. Each flow-reversing passage has aninlet and an outlet. The lateral steering passage is located aft of thedeflector body and reversing passages and has discharge openings onopposite ends thereof, i.e., on the port and starboard sides of thereverse gate. The lateral steering passage communicates with the mainchamber of the reverse gate via an aperture which is centered betweenport and starboard curved outer walls of the reverse gate. These portand starboard curved outer walls extend forward and laterally outward toform the outer side walls of the flow-reversing passages. The centralaperture allows some of the water discharged from the steering nozzle toenter the lateral steering passage. The deflector is situated in frontof the aperture to deflect some of the pump discharge to the sides andinto the flow-reversing passages.

[0009] The deflector body in accordance with the first preferredembodiment of the invention comprises three vertical walls connected ata central vertical line located midway between the reversing passageinlets. The three vertical walls are preferably attached or joined tothe top and bottom walls of the reverse gate housing. One vertical wallof the deflector body lies in the reverse gate midplane and extendsforward from the central juncture of the walls. The other vertical wallsof the deflector body are laterally curved in the shape of respectivearcs. One arc curves from the central juncture toward the inlet of thereversing passage on the port side of the reverse gate; the other arccurves from the central juncture toward the inlet of the reversingpassage on the starboard side of the reverse gate. These curved verticalwalls will be referred to herein as flow-deflecting walls. The concaveside of each flow-deflecting wall faces toward a wide opening in thefront of the reverse gate, through which the water discharged from thesteering nozzle outlet flows into the reverse gate. The flow-deflectingwalls respectively guide or deflect incoming water toward the respectiveinlets of the opposing reversing passages. The incoming stream of wateris split by the central vertical wall into two streams whichrespectively flow along the front surfaces of the curved vertical walls.In accordance with the preferred embodiment, the port surface of thecentral vertical wall and the front surface of the curved vertical wallon the port side form a continuous surface having a J-shaped contourwhich redirects one stream of incoming water toward the port reversingpassage; similarly, the starboard surface of the central vertical walland the front surface of the curved vertical wall on the starboard sideform a continuous surface having a J-shaped contour which redirects theother stream of incoming water toward the starboard reversing passage.

[0010] In accordance with the first preferred embodiment, each curvedvertical wall terminates at a sufficient distance from the opposingcurved outer wall and each curved outer wall is suitably oriented, sothat some water discharged from a steering nozzle steered to one side isdirected by the curved outer wall on that side through the aperture andout the discharge opening on the opposite side of the lateral steeringpassage. Water which flows around the port curved vertical wall of thedeflector body is directed to the starboard discharge opening of thelateral steering passage; while water which flows around the port curvedvertical wall of the deflector body is directed to the starboarddischarge opening of the lateral steering passage.

[0011] The deflector body in accordance with the second preferredembodiment has a shape similar to that of the first embodiment describedabove, i.e., three vertical walls connected at a vertical juncture toform back-to-back J shapes having a common spine. The deflector body ofthe second preferred embodiment differs from the deflector body of thefirst preferred embodiment in two respects: (1) the former is pivotableabout a vertical axis, whereas the latter is fixed; and (2) the lateralspan from the end of the port curved vertical wall to the end of thestarboard curved vertical wall of the former is greater than thecorresponding span of the latter. These differences are related in thatthe ability of the deflector body to pivot in either direction makes itpossible to extend the length of the curved vertical walls withoutdecreasing the gap between the end of the curved vertical wall and thecurved outer wall on the opposite side. The longer laterally curvedvertical walls of the deflector body increase the angle by which theincoming water is turned, direct more water into the flow-reversingpassages. This increases reversing thrust significantly withoutdiminishing the steering thrust.

[0012] For embodiments wherein the deflector body pivots about avertical axis passing through the central vertical wall, the centralvertical wall will be referred to as a leading rudder. When the steeringnozzle is centered, the steering nozzle discharge is split by theleading rudder. The respective streams are then diverted into therespective flow-reversing passages by the respective flow-deflectingwalls of the deflector body. Steering, i.e., turning the steering nozzleabout its pivot axis, in one direction applies unequal forces on the twosides of the deflector body, causing it to pivot in the oppositedirection. This allows some of the nozzle discharge on the other side ofthe leading rudder to miss the deflector body, escape around thebackside, and then flow through the aperture behind the deflector body,into the lateral steering passage, and out the steering passagedischarge opening on the same side toward which the deflector body hasbeen turned. This design produces high steering thrust during flowreversal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is a schematic (presented in two sheets respectivelylabeled FIGS. 1A and 1B) showing a sectional view of a known water jetpropulsion system mounted to a boat hull, the section being taken alonga vertical midplane.

[0014]FIG. 2 is a schematic (presented in two sheets respectivelylabeled FIGS. 2A and 2B) showing a top view of the top mounting plateand the water jet apparatus depicted in FIG. 1, with the hull removed.

[0015]FIG. 3 is a schematic showing a sectional view of the shift andsteering control housing shown in FIG. 2A, the section being taken alongline 3-3 in FIG. 2A.

[0016]FIG. 4 is a schematic showing an isometric view of a reverse gatehaving a fixed deflector body in accordance with one preferredembodiment of the invention.

[0017]FIG. 5 is a schematic showing a front elevational view of thereverse gate depicted in FIG. 4.

[0018]FIG. 6 is a schematic showing a plan view of the reverse gatedepicted in FIGS. 4 and 5. The fixed deflector body is indicated bydashed lines.

[0019]FIG. 7 is a schematic showing a front elevational view of areverse gate having a pivotable deflector body in accordance withanother preferred embodiment of the invention.

[0020]FIGS. 8 and 9 are schematics showing plan views of the reversegate depicted in FIG. 7, with the deflector body in a central position(FIG. 8) and pivoted to starboard (FIG. 9).

[0021]FIG. 10 is a schematic showing a plan view of the reverse gate inaccordance with the second preferred embodiment mounted to a water jetpropulsion system (only partly shown).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]FIGS. 1 and 2 depict a prior water jet propulsion system whichincorporates a steering nozzle and a reverse gate. These drawings show abasic structure for such a system, as well as one possible means forcontrolling the rotational positions of the steering nozzle and thereverse gate. The reverse gate shown in FIGS. 1B and 2B is not part ofthe present invention. The reverse gate in accordance with the preferredembodiments of the invention will be described in detail later withreference to FIGS. 4-10. FIGS. 1-3 are presented for the purpose ofdisclosing exemplary mechanisms for enabling a boat operator to remotelycontrol the positions of a steering nozzle and reverse gate. However, itshould be appreciated that the reverse gate of the invention can beutilized in water jet propulsion apparatus different in structure thanthat shown in FIGS. 1 and 2.

[0023] The water jet propulsion apparatus shown in FIG. 1 is designed tobe installed in a cavity under a section of the hull and in flowcommunication with the outlet of an inlet ramp built into the hull. Asseen in FIG. 1, the boat hull 2 has a inlet ramp 6 formed by a pair ofopposing sidewalls 8 (only one of which is visible in FIG. 1) and aguide surface or ceiling 10 which curves gently upward in the aftdirection. The end of the inlet ramp 6 communicates with a cavity inwhich the water jet propulsion apparatus is installed. This cavity isdefined by a horizontal hull section 12, a vertical hull section 14 anda pair of opposing sidewalls 16 (only one of which is visible in FIG.1), the cavity being open at the bottom and rear to allow insertion ofthe water jet propulsion apparatus.

[0024] The apparatus depicted in FIG. 1 comprises an inlet housing 18,which is slid into the aforementioned cavity and bolted to the hull bymeans of a top mounting plate 20 and a front plate 22. At the time ofinlet housing installation, the drive shaft 26 is already rotatablymounted in the inlet housing. In particular, the inlet housing 18comprises a vertical strut 85 having an axial bore which houses aportion of the drive shaft.

[0025] During inlet housing installation, the front plate 22 is placedon the inside of the vertical hull section 14 and the inlet housing 18is placed on the outside of vertical hull section 14. Screws 24 (onlyone of which is visible in FIG. 1) hold the front plate, vertical hullsection and inlet housing together. The front plate 22 has an opening 34(best seen in FIG. 2) which, in the assembled state, is aligned with anopening 36 in the vertical hull section 14 to allow the output shaft(not shown) from the inboard motor to be coupled to the front end of thedrive shaft 26. The studs 28 are affixed to the inlet housing 18. Theinlet housing 18 is inserted into the hull cavity and the studs 28 areinserted into throughholes in the hull. The front plate 22 is thenpositioned and screws 24 are screwed into the inlet housing 18. The topmounting plate 20 is then placed over the studs 28 and secured to thehull. The top mounting plate 20 has an opening 38 which, in theassembled state, is aligned with an opening 40 in the horizontal hullsection 12 to allow a shift and steering control housing 42 to be placedin a corresponding opening in the top wall of the inlet housing 18.

[0026] The inlet housing 18 has a water tunnel 44 with an inlet 46. Thewater tunnel 44 comprises a pair of sidewalls 48 (only one of which isshown in FIG. 1) which are generally coplanar with the sidewalls 8 ofthe hull inlet ramp 6. In addition, water tunnel 44 comprises a guidesurface 50 which starts at a point near where the guide surface 10 ofthe hull inlet ramp 6 ends and then curves gradually upward in the aftdirection. The hull 2 and the inlet housing 18 combine to form a singleinlet for guiding water toward the inlet of a stator housing 52 locateddownstream of the inlet housing. An inlet grate 54, comprising amultiplicity of generally parallel tines 56, extends across the inlet 46to prevent debris from entering. In addition, a ride plate 58 isattached to the bottom of the inlet housing 18.

[0027] As shown in FIG. 1, the drive shaft projects in the aft directionout of the inlet housing 18. The impeller is pre-assembled in the unitprior to mounting in the hull. The hub and blades of impeller 60 arepreferably integrally formed as one cast piece. The hub of impeller 60has a splined bore which meshes with splines formed on the externalsurface of the drive shaft 26, so that the impeller 60 will rotate inunison with the drive shaft. The impeller 60 is held on a threaded endof the drive shaft 26 by a threaded nut 64.

[0028] The stator housing 52 comprises inner and outer shells connectedby a plurality of stator vanes, all integrally formed as a single castpiece. The stator vanes are designed to redirect the swirling flow outof the impeller 60 into non-swirling flow. A tail cone cover 66 isattached to the radial end face of the stator housing hub. The front ofthe stator housing 52 is then attached to the rear of the inlet housing18. A circumferential recess in the stator housing 52 at a positionopposing the impeller blade tips has a circular cylindrical wear ring 65seated therein.

[0029] An exit nozzle 70 is attached to and in flow communication withthe stator housing 52. Water from the stator housing 52 flows throughthe space between the tail cone cover 66 and the exit nozzle 70. Asteering nozzle 72 is pivotably mounted to the exit nozzle 70 by a pairof pivot assemblies 74 and 76 having collinear axes. The steering nozzle72 can be turned to change the direction of the water being dischargedfrom the exit nozzle 70.

[0030] As best seen in FIG. 2B, the steering nozzle 72 has an arm 68which is pivotably coupled to a flattened end of a steering rod 114.Displacement of the steering rod 114 in response to operation of asteering cable assembly 78 (see FIG. 2A) causes the steering nozzle 72to swing in a desired direction about its vertical pivot axis.

[0031] The water jet apparatus shown in FIGS. 1 and 2 is provided with anon-steerable reverse gate 80, best seen in FIG. 2B. In the forwardposition, the reverse gate 80 is raised, thereby allowing water to exitthe steering nozzle 72 freely. In the reverse position, the reverse gate80 is lowered to a position directly opposite to the outlet of thesteering nozzle 72. The reverse gate is designed to partially reversethe flow of water exiting the steering nozzle 72 when the reverse gateis in the reverse position. To accomplish the foregoing, the arms 98 and100 of the reverse gate 80 are pivotably mounted to a pair of pivotassemblies 94 and 96 located on opposite sides of the exit nozzle 70(see FIG. 2B). The support arms 98 and 100 are rigid members whichconnect to the exit nozzle 70. The reverse gate 80 is pivoted by a shiftrod 92, the end of which is coupled to arm 98 of the reverse gate 80 bymeans of a rod end assembly 102 which comprises a ball socket forallowing horizontal radial motion at the shift lever and vertical radialmotion at the reverse gate. The rod end assembly is attached to arm 98by means of a screw 104 and a lock nut 106. Displacement of the shiftrod 92 in response to operation of a shift cable assembly 82 (see FIG.2A) causes the reverse gate to swing in a desired direction, namely,into forward position or reverse position, with a “neutral” positiontherebetween.

[0032] In the apparatus depicted in FIGS. 1 and 2, the shift andsteering cable assemblies (located inside the hull) are respectivelycoupled to shift and steering rods (located outside the hull) by meansof respective lever and shaft assemblies rotatably supported in a shiftand steering control housing 42 which penetrates the hull. The shift andsteering control housing 42 is installed in a corresponding opening inthe top of the inlet housing 18. As seen in FIG. 2A, the housing 42preferably comprises a base plate 116; as best seen in FIG. 3, thehousing 42 further comprises an upper vertical tubular structures 118and 120 extending above the base plate to different heights. The tubularstructures 118 and 120 are reinforced by a rib 122. Additionalreinforcement is provided by respective pairs of ribs visible in FIG.2A. Referring again to FIG. 3, below the base plate 116, the housing hasa circular cylindrical lower wall 128 integrally formed with lowervertical tubular structures 130 and 132. The lower wall 128 slides intoa circular opening formed in the top wall of the inlet housing 18. Theopening in the inlet housing communicates with the exterior of the waterjet apparatus via a pair of opposing side channels through which thelower shift and steering levers (described below) respectively pass.Preferably the opening 40 (see FIG. 1A) in the horizontal hull section12 closely matches the opening in mounting plate. As seen in FIG. 2A,the housing 42 is bolted to the inlet housing 18.

[0033] As seen in FIG. 3, the shift and steering control housing 42 hasone bore 146 for receiving the shift shaft 88 and another bore 148 forreceiving the steering shaft 110. The bore 146 has upper and lowerannular recesses in which upper and lower bushings 150 and 152 arerespectively inserted; the bore 148 has upper and lower annular recessesin which upper and lower bushings 154 and 156 are respectively inserted.The shift shaft 88 is rotatably supported in bushings 150 and 152, whilesteering shaft 110 is rotatably supported in bushings 154 and 156. Oneend of the upper shift lever 86 is secured to the top of the shift shaft88 by means of a lock nut 158 which screws onto a threaded end of theshift shaft; one end of the upper steering lever 108 is secured to thetop of the steering shaft 110 by means of a lock nut 160 which screwsonto a threaded end of the steering shaft. (Only a portion of each ofthe upper levers is shown in FIG. 3.) The upper levers bear on theflanges of the upper bushings during rotation of the lever and shaftassemblies.

[0034] Still referring to FIG. 3, a lower shift lever 90 is welded tothe bottom of the shift shaft 88, while a lower steering lever 112 iswelded to the bottom of the steering shaft 110. A lower washer 178 isinstalled between the lower shift lever 90 and the lower verticaltubular structure 130 of the shift and steering control housing 42,while a lower washer 180 is installed between the lower steering lever112 and the lower vertical tubular structure 132 of housing 42. Thewashers 178 and 180 provide a bearing surface. During assembly, thebottoms of the shafts are supported by a boss 138. The full length ofthe lower steering lever 112 is shown in FIG. 3, while only a portion ofthe lower shift lever 90 is depicted. FIG. 3 shows a clevis 182 and ashoulder screw 184 for attaching the distal end of the lower steeringlever 112 to the forward end of the steering rod (not shown in FIG. 3).Similarly, the distal end of the lower shift lever is attached to theforward end of the shift rod by means of a clevis and shoulder screwcoupling (not shown in FIG. 3).

[0035] Referring to FIG. 2A, the distal end of the upper shift lever 86is attached to the shift cable assembly 82 by means of a clevis 186 anda clevis pin 188. These components are located inside the hull of theboat (see FIG. 1A). Displacement of the end of the shift cable assemblycauses the shift lever and shaft assembly to rotate. Likewise the distalend of the upper steering lever 108 is attached to the steering cableassembly 78 by means of a clevis 190 and a clevis pin 192, anddisplacement of the end of the steering cable assembly causes thesteering lever and shaft assembly to rotate. As best seen in FIG. 1A,the shift cable assembly 82 is supported by a bracket 194 and thesteering cable assembly 78 is supported by a bracket 196, both bracketsbeing integrally connected to and extending vertically upward from thetop mounting plate 20. In response to operation of the steering cableassembly 78, the steering nozzle can be selectively turned left or rightto steer the boat as desired during water jet operation. In response tooperation of the shift cable assembly 82, the reverse gate can beselectively raised or lowered.

[0036] In accordance with the preferred embodiments of the invention,the reverse gate is pivotably mounted to an exit nozzle or to anintegral stator housing/exit nozzle, and is pivotable between first andsecond shift positions. The reverse gate in the first shift position isremoved from the path of water exiting the exit nozzle and in the secondshift position is disposed in the path of water exiting the exit nozzle.Reverse gates in accordance with first and second preferred embodimentsof the invention are shown in FIGS. 4-6 and in FIGS. 7-10 respectively,with the pivot pin assemblies and the shift rod assembly for deployingthe reverse gate not shown. As seen in those drawings, the housings forthe two embodiments are substantially the same, while the majordifference between the embodiments lies in the deflector body, which isfixed in the first embodiment and freely pivotable between limit stopsin the second embodiment. Although not shown in the drawings, theinvention also encompasses coupling the pivotable deflector body to thesteering nozzle or to the means for turning the steering nozzle. Thedeflector body would be coupled to pivot in a direction opposite to thedirection in which the steering nozzle was pivoted.

[0037] As seen in FIG. 4, pivot pins for pivotably supporting thereverse gate would be received in coaxial pivot holes 196 and 196′formed in mounting walls 198 and 198′ respectively. The pivot pins 197are shown in FIG. 10. The centerlines of the pivot pins 197 define thepivot axis. The reverse gate is deployed by actuating the previouslydescribed shifting rod (92 in FIG. 2B), which is coupled to the clevis244 mounted to the top wall 210 of the reverse gate. The fully downposition of the reverse gate is shown in FIG. 10. Preferably, thereverse gate is pivotably coupled to the ends of a pair of support arms200 and 200′ which extend from an integral stator housing/exit nozzle202. The steering nozzle 204 is pivotably mounted to the exit nozzle bymeans of pivot pins 205, one of which is visible in FIG. 10. The reversegate must be shaped to provide clearance between it and the steeringnozzle during deployment.

[0038] The reverse gates shown in FIGS. 4-10 each comprise port andstarboard flow-reversing passages 206 and 206′ having respectivedischarge openings 208 and 208′. As seen in FIGS. 5 and 7, the distalsections of the flow-reversing passages 206 and 206′ are splayeddownward and outward. Each of the flow-reversing passages 206 and 206′may have a generally rectangular cross section with sharp or roundedcorners. In particular, the flow-reversing passages 206 and 206′ aredefined by respective portions of the top wall 210, respective portionsof the bottom wall 212, respective portions of the port and starboardcurved outer walls 214 and 214′, and the port and starboard inner sidewalls 216 and 216′ respectively.

[0039] In accordance with the preferred embodiments of the invention,the reverse gate further comprises a lateral steering passage 218 forproducing a lateral thrust when the steering nozzle is turned. As bestseen in FIGS. 6 and 8, the lateral steering passage 218 is located aftof the deflector body and reversing passages and has discharge openings220 and 220′ on opposite ends thereof, i.e., on the port and starboardsides of the reverse gate. The lateral steering passage 218 comprises anaft wall 222 which is laterally straight and aft portions of the topwall 210 and the bottom wall 212. The discharge openings 220 and 220′are defined by edges of the same walls in conjunction with respectiveportions of the curved outer walls 214 and 214′, as seen in FIGS. 6 and8. The lateral steering passage 218 communicates with the main chamberof the reverse gate via an aperture 224 which is centered between portand starboard curved outer walls 214 and 214′ of the reverse gate. Thecurved outer walls 214 and 214′ extend forward and laterally outward toform the outer side walls of the flow-reversing passages 206 and 206′,respectively. The central aperture 224 allows some of the waterdischarged from the steering nozzle to enter the lateral steeringpassage 218.

[0040] As seen in FIGS. 5 and 7, in both embodiments a deflector body226 is situated behind the front opening 228 in the reverse gatehousing. The deflector body 226 is designed to split the incoming waterdischarged from the steering nozzle and divert the resulting streams tothe port and starboard sides and toward the respective flow-reversingpassages 206 and 206′.

[0041] Referring to FIG. 6, the deflector body 226 in accordance withthe first preferred embodiment comprises three vertical walls 230, 232and 234, connected along a vertical line to form a central juncture 236.The central juncture is located midway between the reversing passageinlets. The three vertical walls are preferably attached or joined tothe top and bottom walls of the reverse gate housing. The flow-splittingwall 230 of the deflector body is longitudinally straight and preferablyplanar. The flow-splitting wall 230 lies in the reverse gate midplaneand extends forward from the central juncture 236 of the walls. Theflow-deflecting walls 232 and 234 of the deflector body are laterallycurved in the shape of respective arcs. One arc 232 curves from thecentral juncture 236 toward the inlet of the reversing passage 206 onthe port side of the reverse gate; the other arc 234 curves from thecentral juncture 236 toward the inlet of the reversing passage 206′ onthe starboard side of the reverse gate. The concave side of eachflow-deflecting wall 232 and 234 faces toward the opening 228 in thefront of the reverse gate. The flow-deflecting walls 232 and 234respectively guide or deflect incoming water toward the respectiveinlets of the opposing reversing passages 206 and 206′. The incomingstream of water is split by the flow-splitting wall 230 into two streamswhich respectively flow along the front surfaces of the flow-deflectingwalls 232 and 234. The port surface of the flow-splitting wall 230 andthe front surface of the flow-deflecting wall 232 on the port side forma continuous surface having a J-shaped contour which redirects onestream of incoming water toward the port reversing passage 206;similarly, the starboard surface of the flow-splitting wall 230 and thefront surface of the flow-deflecting wall 234 on the starboard side forma continuous surface having a J-shaped contour which redirects the otherstream of incoming water toward the starboard reversing passage 206′.

[0042] In accordance with the first preferred embodiment, eachflow-deflecting wall 232 or 234 terminates at a sufficient distance fromthe opposing curved outer wall 216 and 216′, and each curved outer wall214 and 214′ is suitably oriented, so that some water discharged fromthe steering nozzle, when the latter is steered to one side, is directedby the curved outer wall on that side, through the aperture and out thedischarge opening on the opposite side of the lateral steering passage.For instance, water which flows around the flow-deflecting wall 232 isdirected to the starboard discharge opening 220′ of the lateral steeringpassage; while water which flows around the flow-deflecting wall 234 isdirected to the port discharge opening 220 of the lateral steeringpassage.

[0043] Thus the reverse gate in accordance with the first preferredembodiment shown in FIGS. 4-6 is able to produce reverse thrust andlateral steering thrust, the latter being directed so that the boatsteers in reverse like an automobile.

[0044] The deflector body in accordance with the second preferredembodiment, shown in FIGS. 7-9, has a shape similar to that of the firstembodiment described above, i.e., three vertical walls connected at avertical juncture to form back-to-back J shapes having a common spine.The deflector body of the second preferred embodiment differs from thedeflector body of the first preferred embodiment in two respects: (1)the deflector body of the second embodiment is freely pivotable about avertical axis between limit stops (the limit position is shown in FIG.9), whereas the deflector body of the first embodiment was fixed; and(2) the angle of curvature (and lateral span) of each flow-deflectingwall of the second embodiment is greater than the angle of curvature(and lateral span) of the flow-deflecting walls of the first embodiment.These differences are related: pivoting of the deflector body in eitherdirection makes it possible to extend the length of the flow-deflectingwalls without decreasing the gap between the end of one flow-deflectingwall and the opposing curved outer wall 214 or 214′. Any decrease in thegap length would decrease the volume of water which can flow through thegap, other factors being equal. Also, the greater angle of curvature ofthe flow-deflecting walls allows more water to be diverted toward theflow-reversing passages. This increases reversing thrust significantlywithout diminishing the steering thrust.

[0045] In the case of a pivoting deflector body, the flow-splittingvertical wall 238 acts as a leading rudder. The leading rudder 238 ispivotably coupled to a pair of pivot pins 240 and 242, as shown in FIG.7. Alternatively, the leading rudder can be mounted to a pivot shaftwhich passes through the leading rudder, the axis of the shaft lying inthe plane of the rudder. Each of the flow-deflecting walls 232′ and 234′extends along a circular arc having an angle greater than the arc anglein the first embodiment. The deflector body is pivotable about avertical pivot axis between limit positions (one of which is shown inFIG. 9) dictated by limit stops strategically placed on the port andstarboard sides of the reverse gate housing. For example, limit stops(not shown) may be integrally formed on the top or bottom wall of eachflow-reversing passage.

[0046] The reverse gate in accordance with the second preferredembodiment operates as follows. When the steering nozzle 72 is centeredas shown in FIG. 8, the steering nozzle discharge is split by theleading rudder 238. The respective streams are then diverted toward therespective flow-reversing passages 206 and 206′ by the respectiveflow-deflecting walls 232 and 234 of the deflector body. Steering, i.e.,turning the steering nozzle about its pivot axis, in one directionapplies unequal forces on the two sides of the deflector body, causingit to pivot in the opposite direction. The leading rudder 238 stillsplits the incoming stream in two. The major portion of the nozzledischarge is directed to the side toward which the steering nozzle isturned; the remainder of the nozzle discharge is directed by the leadingrudder to the opposite side. Because the deflector body is now turned,the tips of the flow-deflecting walls 232 and 234 are not symmetricallylocated. There is a large gap between the tip of the flow-deflectingwall in the path of the major stream, while the gap on the other side issubstantially closed. In the example shown in FIG. 9, one part of themajor stream is diverted toward the flow-reversing passage 206 on theport side; another part of the major stream will flow through the gapbetween the flow-deflecting wall 232 and the opposing outer curved wall214 and then out the steering passage discharge opening 220′ on thestarboard side. Conversely, the majority of the nozzle discharge willflow out the discharge opening of the starboard flow-reversing passageand the port discharge opening of the steering passage when the steeringnozzle is turned to starboard. This design produces high reverse thrustand high lateral steering thrust when the boat is shifted into reverse.

[0047] The deflector body in accordance with the preferred embodimentscomprises a pair of vertical surfaces. One vertical surface extendsstraight from a first point adjacent the front opening to a second pointlocated rearward of the first point and then curves along an arc fromthe second point to a third point. The other vertical surface extendsstraight from a fourth point adjacent the front opening to a fifth pointlocated rearward of the fourth point and then curves along an arc fromthe fifth point to a sixth point. The first and fourth points areseparated by the thickness of the leading edge of the deflector body.The arcs are equal to each other and preferably greater than 90 degrees.The third and sixth points are symmetrically located on opposing sidesof a plane of symmetry defined by a plane midway between the straightportions of the vertical surfaces. The transitions from the straightportions to the curved portions at the second and fifth points aresmooth. The deflector body preferably pivots freely over a range ofangles dictated by the location of the limit stops. Alternatively, thepivotable deflector body may be coupled to have an angular positionwhich is a function of the angular position of the steering nozzle.

[0048] While the invention has been described with reference topreferred embodiments, it will be understood by those skilled in the artthat various changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationto the teachings of the invention without departing from the essentialscope thereof. Therefore it is intended that the invention not belimited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

[0049] As used in the claims, the term “longitudinal” refers to adirection generally parallel to the centerline axis of a water jetpropulsion system; the term “lateral” refers to a direction generallyperpendicular to the longitudinal direction and generally parallel to areverse gate pivot axis; and the term “vertical” refers to a directiongenerally perpendicular to the plane defined by the longitudinal andlateral axes. Also, as used in the claims, the term “duct” may comprisea single part or a plurality of assembled parts. For example, in thedisclosed preferred embodiment, the inlet housing, stator housing andexit nozzle form a “duct”. However, the present invention encompassesforming the inlet housing and stator housing as one piece, forming thestator housing and the exit nozzle as one piece, forming the inlethousing as two pieces, forming the stator housing as two pieces, and soforth. All such variations fall within the meaning of “duct” as thatterm is used in the claims.

1. A reverse gate comprising: a housing having a front opening andcomprising first and second flow-reversing passages arranged on opposingsides thereof, each of said first and second flow-reversing passageshaving an inlet and a discharge opening, and a lateral steering passagelocated in a rear portion of said housing, said lateral steering passagehaving discharge openings at opposite ends thereof; and a deflector bodyarranged inside said housing, said deflector body comprising a straightvertical wall and first and second curved vertical walls, each of saidvertical walls being connected to a juncture, said straight verticalwall extending forward from said juncture, and said first and secondcurved vertical walls extending rearward and laterally outward from saidjunction, said first and second curved vertical walls extending alongarcs on opposite sides of a plane which is generally co-planar with saidstraight vertical wall, the concave sides of said curved vertical wallsgenerally facing said front opening and the convex sides of said curvedvertical walls generally facing said lateral steering passage.
 2. Thereverse gate as recited in claim 1, wherein said deflector body ispivotably mounted to said housing.
 3. The reverse gate as recited inclaim 2, further comprising a pair of pivot pins coupled to saidstraight vertical wall for pivotably mounting said deflector body tosaid housing.
 4. The reverse gate as recited in claim 2, wherein saiddeflector body pivots freely over a predetermined range of angles. 5.The reverse gate as recited in claim 1, wherein said straight verticalwall and said first curved vertical wall form a J shape.
 6. The reversegate as recited in claim 1, wherein said first and second curvedvertical walls have shapes which mirror each other.
 7. The reverse gateas recited in claim 1, wherein said housing comprises top and bottomwalls connected by first and second curved outer walls on opposing sidesthereof, forward portions of said first and second curved outer wallsforming portions of said first and second flow-reversing passagesrespectively, and rear portions of said first and second curved outerwalls partly forming said discharge openings of said lateral steeringpassage.
 8. The reverse gate as recited in claim 7, wherein said firstand second curved vertical walls have distal ends which do not contactsaid first and second curved outer walls respectively.
 9. A reverse gatecomprising: a housing having a front opening and comprising first andsecond flow-reversing passages arranged on opposing sides thereof, eachof said first and second flow-reversing passages having an inlet and adischarge opening, and a lateral steering passage located in a rearportion of said housing, said lateral steering passage having dischargeopenings at opposite ends thereof; and a deflector body arranged insidesaid housing, said deflector body comprising first and second verticalsurfaces, said first vertical surface extending straight from a firstpoint adjacent said front opening to a second point located rearward ofsaid first point and then curving along a first arc from said secondpoint to a third point, and said second vertical surface extendingstraight from a fourth point adjacent said front opening to a fifthpoint located rearward of said fourth point and then curving along asecond arc from said fifth point to a sixth point, wherein said firstand fourth points are separated by a thickness of a leading edge of saiddeflector body, said first and second arcs are equal to each other, andsaid third and sixth points are symmetrically located on opposing sidesof a plane of symmetry defined by a plane midway between said straightportions of said first and second vertical surfaces.
 10. The reversegate as recited in claim 9, wherein the transitions from said straightportions to said curved portions at said second and fifth points aresmooth.
 11. The reverse gate as recited in claim 9, wherein said firstand second arcs are each greater than 90 degrees.
 12. The reverse gateas recited in claim 9, wherein said deflector body is pivotably mountedto said housing.
 13. The reverse gate as recited in claim 12, furthercomprising a pair of pivot pins coupled to said deflector body along asection having said straight portions on opposing sides thereof.
 14. Thereverse gate as recited in claim 12, wherein said deflector body pivotsfreely over a predetermined range of angles.
 15. The reverse gate asrecited in claim 9, wherein each of said first and second verticalsurfaces forms a J shape.
 16. The reverse gate as recited in claim 9,wherein said housing comprises top and bottom walls connected by firstand second curved outer walls on opposing sides thereof, forwardportions of said first and second curved outer walls forming portions ofsaid first and second flow-reversing passages respectively, and rearportions of said first and second curved outer walls partly forming saiddischarge openings of said lateral steering passage.
 17. The reversegate as recited in claim 9, wherein a distal end of said curved portionof said first vertical surface is directed toward said inlet of saidfirst flow-reversing passage, and a distal end of said curved portion ofsaid second vertical surface is directed toward said inlet of saidsecond flow-reversing passage.
 18. A water jet propulsion systemcomprising: a duct having an inlet and an outlet; an impeller which isrotatable within said duct; a steering nozzle pivotably mounted to anoutlet end of said duct and having an inlet and an outlet, said steeringnozzle being pivotable between first and second steering positions, andsaid steering nozzle inlet being in flow communication with said ductoutlet; and a reverse gate pivotably mounted to said duct, said reversegate being pivotable about a pivot axis between first and second shiftpositions, said reverse gate in said first shift position being removedfrom the path of water exiting said steering nozzle outlet and in saidsecond shift position being in the path of water exiting said steeringnozzle outlet, wherein said reverse gate comprises: a housing having afront opening which faces said steering nozzle outlet when said reversegate is in said second shift position, said housing comprising first andsecond flow-reversing passages arranged on opposing sides thereof, eachof said first and second flow-reversing passages having an inlet and adischarge opening, and a lateral steering passage located in an aftportion of said housing, said lateral steering passage having dischargeopenings at opposite ends thereof; and a deflector body arranged insidesaid housing, said deflector body comprising a straight vertical walland first and second curved vertical walls, each of said vertical wallsbeing connected to a juncture, said straight vertical wall extendingforward from said juncture, and said first and second curved verticalwalls extending rearward and laterally outward from said junction, saidfirst and second curved vertical walls extending along arcs on oppositesides of a plane which is generally co-planar with said straightvertical wall, the concave sides of said curved vertical walls generallyfacing said front opening and the convex sides of said curved verticalwalls generally facing said lateral steering passage.
 19. The water jetpropulsion system as recited in claim 18, wherein said deflector body ispivotably mounted to said housing.
 20. The water jet propulsion systemas recited in claim 19, wherein said deflector body pivots freely over apredetermined range of angles.
 21. The water jet propulsion system asrecited in claim 18, wherein said housing comprises top and bottom wallsconnected by first and second curved outer walls on opposing sidesthereof, forward portions of said first and second curved outer wallsforming portions of said first and second flow-reversing passagesrespectively, and rear portions of said first and second curved outerwalls partly forming said discharge openings of said lateral steeringpassage.
 22. A water jet propulsion system comprising: a duct having aninlet and an outlet; an impeller which is rotatable within said duct; asteering nozzle pivotably mounted to an outlet end of said duct andhaving an inlet and an outlet, said steering nozzle being pivotablebetween first and second steering positions, and said steering nozzleinlet being in flow communication with said duct outlet; and a reversegate pivotably mounted to said duct, said reverse gate being pivotableabout a pivot axis between first and second shift positions, saidreverse gate in said first shift position being removed from the path ofwater exiting said steering nozzle outlet and in said second shiftposition being in the path of water exiting said steering nozzle outlet,wherein said reverse gate comprises: a housing having a front openingwhich faces said steering nozzle outlet when said reverse gate is insaid second shift position, said housing comprising first and secondflow-reversing passages arranged on opposing sides thereof, each of saidfirst and second flow-reversing passages having an inlet and a dischargeopening, and a lateral steering passage located in an aft portion ofsaid housing, said lateral steering passage having discharge openings atopposite ends thereof; and a deflector body pivotably mounted insidesaid housing.
 23. The water jet propulsion system as recited in claim22, wherein said deflector body pivots freely over a predetermined rangeof angles.
 24. The water jet propulsion system as recited in claim 22,wherein said deflector body comprises a straight vertical wall and firstand second curved vertical walls, each of said vertical walls beingconnected to a juncture, said straight vertical wall extending forwardfrom said juncture, and said first and second curved vertical wallsextending rearward and laterally outward from said junction, said firstand second curved vertical walls extending along arcs on opposite sidesof a plane which is generally co-planar with said straight verticalwall, the concave sides of said curved vertical walls generally facingsaid front opening and the convex sides of said curved vertical wallsgenerally facing said lateral steering passage.
 25. The water jetpropulsion system as recited in claim 22, wherein said deflector bodycomprises first and second vertical surfaces, said first verticalsurface extending straight from a first point adjacent said frontopening to a second point located rearward of said first point and thencurving along a first arc from said second point to a third point, andsaid second vertical surface extending straight from a fourth pointadjacent said front opening to a fifth point located rearward of saidfourth point and then curving along a second arc from said fifth pointto a sixth point, wherein said first and fourth points are separated bya thickness of a leading edge of said deflector body, said first andsecond arcs are equal to each other, and said third and sixth points aresymmetrically located on opposing sides of a plane of symmetry definedby a plane midway between said straight portions of said first andsecond vertical surfaces.
 26. A water jet propulsion system comprising:a duct having an inlet and an outlet; an impeller which is rotatablewithin said duct; a steering nozzle pivotably mounted to an outlet endof said duct and having an inlet and an outlet, said steering nozzlebeing pivotable between first and second steering positions, and saidsteering nozzle inlet being in flow communication with said duct outlet;and a reverse gate pivotably mounted to said duct, said reverse gatebeing pivotable about a pivot axis between first and second shiftpositions, said reverse gate in said first shift position being removedfrom the path of water exiting said steering nozzle outlet and in saidsecond shift position being in the path of water exiting said steeringnozzle outlet, wherein said reverse gate comprises: a housing having afront opening which faces said steering nozzle outlet when said reversegate is in said second shift position, said housing comprising first andsecond flow-reversing passages arranged on opposing sides thereof, eachof said first and second flow-reversing passages having an inlet and adischarge opening, and a lateral steering passage located in an aftportion of said housing, said lateral steering passage having dischargeopenings at opposite ends thereof; and a deflector body mounted insidesaid housing, said deflector body comprising first and second verticalsurfaces, said first vertical surface extending straight from a firstpoint adjacent said front opening to a second point located rearward ofsaid first point and then curving along a first arc from said secondpoint to a third point, and said second vertical surface extendingstraight from a fourth point adjacent said front opening to a fifthpoint located rearward of said fourth point and then curving along asecond arc from said fifth point to a sixth point, wherein said firstand fourth points are separated by a thickness of a leading edge of saiddeflector body, said first and second arcs are equal to each other, andsaid third and sixth points are symmetrically located on opposing sidesof a plane of symmetry defined by a plane midway between said straightportions of said first and second vertical surfaces.